The invention relates to a process and composition for the thinning of fruit blooms, and more particularly to the use of a calcium chloride solution for the natural thinning of fruit blossoms.
Under most conditions, fruit and nut trees will produce an over-abundant crop. This over production results in small, low quality fruit, often poorly colored. The thinning of fruit blossoms prevents this over-production and promotes annual bearing, instead of fruit production that fluctuates year to year. Thinning also increases fruit size and color. For fruit trees, bloom thinning also increases tree vigor, and reduces limb breakage and winter injury. Because of these benefits, chemical bloom thinning practices are quite common, but are expensive and must be applied with care.
Most conventional chemical products employed for the thinning of blossoms on plants such as fruit trees can produce unwanted effects beyond thinning. Chemical thinning uses either caustic materials or hormonal type growth regulators to reduce the quantity of fruit in a particular crop. Most hormonal type thinners are quickly losing acceptance, with many hormonal thinners currently banned or under the scrutiny of several groups concerned about effects on the products to which they are applied. Caustic thinners either employ weakly acidic compounds or desiccating formulations to chemically dry or xe2x80x9cburnxe2x80x9d the blossoms. Bloom desiccation apparently prevents pollination and inhibits seed formation.
Generally, thinning is a naturally occurring phenomenon for most food crops. The variety and strain of the plant or tree, health and proximity to pollenizers all dictate the fruit xe2x80x9csetxe2x80x9d or quantity of blooms that can develop into a mature fruit. Additionally, climatic factors, such as wind, precipitation, and primarily temperature can all act as natural thinners to reduce the number of blooms available for pollination and eventual maturation into a salable product. However, natural thinning is unreliable and inconsistent, especially in moderate climates.
Consistent and controlled thinning is especially critical in fruit tree crops, where each fruit competes for resources from the tree. Too high of a fruit set on individual trees drastically reduces the size of each fruit and so reduces the sizing grade of the crop. Failure to make a sizing grade can eliminate any chance of profit for an orchardist.
For fruit trees, only a limited number of caustic chemical bloom thinners are currently available or in the registration process. The pursuit of registration through the United States Environmental Protection Agency (USEPA) can be a long and expensive process. The typical orchardist has few options in thinning. Fewer still are the thinning options available to organic orchardists, which cannot utilize any compound that fails to acquire an xe2x80x9call naturalxe2x80x9d designation.
For fruit trees, manual thinning can be performed to reduce or eliminate the need for chemical thinners. However, the expense of manual thinning is considerable and the availability of skilled workers that can efficiently thin tree fruits decreases every year. Effective and affordable chemical bloom thinning alternatives are needed for both the conventional and organic orchardist.
In Washington state, for example, fruit tree crops such as apples may soon be allowed to employ ammonium thiosulfate (ATS) for bloom thinning. ATS is considered a generally effective and consistent caustic chemical type of bloom thinner. However, ATS is not classified a natural or xe2x80x9corganicxe2x80x9d compound and so cannot be used by organic orchards.
A combination of fish oil and lime sulfur is an alternative to ATS that currently meets the criteria for use as an organic compound. A significant problem encountered with fish oil and lime sulfur is that the results of any particular application can vary considerably. Applications of fish oil and lime sulfur are not repeatable to produce the same effect under what appear to be identical conditions. According to field trials by the Washington Tree Fruit Research Commission, damage from fish oil and lime sulfur can result in a wide range of effects that can include significant over-thinning and injury to the developing fruit and leaves, such as russeting and wilting. Alarmingly, the same treatment of the caustic oil/sulfur mix, which injured fruit under similar conditions, may at another time produce no measurable fruit thinning effects at all. A chemical fruit thinner, which relies on caustic rather than hormonal mechanisms to thin fruit, is needed that provides consistent and predictable thinning results.
Naphthaleneacetic acid (NAA) is a widely utilized chemical bloom thinner that employs the hormonal and acidic properties of the compound to thin the blossoms. NAA was first used to delay preharvest drop and then later found to be an effective bloom thinner. Similar to NAA is napthaleneacetamide (NAD or NAAm). Both NAA and NAD are often combined with the insecticide Carbaryl to increase the efficacy of the thinners. This combination is especially worrisome, in that Carbaryl, which is sold under the trade name Sevin(copyright), is toxic to bees, predatory mites and most importantly, farm workers
Prior U.S. patents that cite fruit thinning properties for caustic type fruit thinning agents include U.S. Pat. No. 3,958,007 to Wommack, which teaches the pesticidal use of a particular family of substituted alkyl, 4-3-thioallophanates. Additionally, Wommack suggests that a salt of these substituted compounds can be applied in a mixture with thinning compounds. U.S. Pat. No. 5,118,340 to Butselaar ""340 discloses that the chloride salts of alkoxylated amines can thin the blossoms of certain stone fruits. These prior patents employ salts of the active ingredients to better achieve solution into water for application. These previously disclosed active ingredients may be effective compounds for thinning fruits, especially tree fruits. Like the currently utilized chemical bloom thinners, these patents suggest compounds that are expensive to synthesize or separate. Importantly, none of these prior bloom thinning compounds include a guarantee of environmental safety nor are they intrinsically free of unwanted effects, beyond their intended purpose.
The present invention provides a process and composition for thinning fruit blossoms with a calcium chloride solution. The calcium chloride salt is actually a di-chloride, having a chemical formula of CaCl2. Calcium chloride is preferably applied to the blooms in a solution or brine. The calcium chloride brine, applied by the present invention, is a natural material that is classified as a xe2x80x9cgenerally regarded as safexe2x80x9d (GRAS) compound. The calcium chloride solution in water has the apparent ability to interrupt the pollination of blooms through the dessication of the pistils, when it is applied during the blooming period. The CaCl2 blossom or bloom thinning agent solution is effective on many varieties of fruit bearing plants, especially fruit bearing trees, such as apple trees.
The present invention thins fruit blossoms by applying an effective amount of the blossom thinning composition to the blossoms of a fruit bearing plant. The blossom thinning composition includes calcium chloride (CaCl2) as an active ingredient for the purpose of blossom thinning. The calcium chloride is preferably applied in a substantially aqueous solution, at a rate of between 5 and 40 pounds of calcium chloride per acre of the fruit bearing plant. A preferred, final mixture of the calcium chloride includes approximately 1 pound of CaCl2 per 10 gallons of water.
The CaCl2 solution applied to blossoms by the present invention has a great advantage over other, conventional thinning agents in that it is not an artificial or derived substance and carries none of the environmental and health concerns raised by other hormonal or caustic chemical thinning agents.